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Subject: Re: [PATCH] net/mlx4_en: Fix an error handling path in
 'mlx4_en_init_netdev()'
To:     Dan Carpenter <dan.carpenter@oracle.com>,
        Yuval Shaia <yuval.shaia@oracle.com>
Cc:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        davem@davemloft.net, tariqt@mellanox.com, netdev@vger.kernel.org,
        linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org
References: <20180510070226.19575-1-christophe.jaillet@wanadoo.fr>
 <20180510133808.GA10943@lap1> <20180510141836.2qlm676j4675buti@mwanda>
From:   Tariq Toukan <tariqt@mellanox.com>
Message-ID: <f29e851d-c4d7-cd04-dbb7-582adebc2854@mellanox.com>
Date:   Thu, 10 May 2018 17:36:55 +0300
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On 10/05/2018 5:18 PM, Dan Carpenter wrote:
> On Thu, May 10, 2018 at 04:38:08PM +0300, Yuval Shaia wrote:
>> On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
>>> If an error occurs, 'mlx4_en_destroy_netdev()' is called.
>>> It then calls 'mlx4_en_free_resources()' which does the needed resources
>>> cleanup.
>>>
>>> So, doing some explicit kfree in the error handling path would lead to
>>> some double kfree.
>>
>> Patch make sense but what's bothering me is that mlx4_en_free_resources
>> loops on the entire array, assuming !priv->tx_ring[t] means entry is
>> allocated but the existing code does not assume that, see [1]. So i looked
>> to see where tx_ring array is zeroed and didn't find it.
>>
>> Am i missing something here.
>>
> 
> It's zeroed twice.  alloc_etherdev_mqs() allocates zeroed memory and
> then we do a memset(priv, 0, sizeof(struct mlx4_en_priv));
> 
> regards,
> dan carpenter
> 

We do zero (twice) on init, that's right. But I think Yuval's comment is 
valid in case of the driver went into configuration change, or down/up, 
that reallocates the rings. I'm double checking this.